diff --git a/lib/schemaType.js b/lib/schemaType.js
index ee8c9a6aeeb..ae64712f823 100644
--- a/lib/schemaType.js
+++ b/lib/schemaType.js
@@ -59,7 +59,9 @@ function SchemaType(path, options, instance) {
   const defaultOptionsKeys = Object.keys(defaultOptions);
 
   for (const option of defaultOptionsKeys) {
-    if (defaultOptions.hasOwnProperty(option) && !Object.prototype.hasOwnProperty.call(options, option)) {
+    if (option === 'validate') {
+      this.validate(defaultOptions.validate);
+    } else if (defaultOptions.hasOwnProperty(option) && !Object.prototype.hasOwnProperty.call(options, option)) {
       options[option] = defaultOptions[option];
     }
   }
diff --git a/test/schematype.test.js b/test/schematype.test.js
index 38691d645ae..582a135c09c 100644
--- a/test/schematype.test.js
+++ b/test/schematype.test.js
@@ -208,6 +208,37 @@ describe('schematype', function() {
     });
   });
 
+  it('merges default validators (gh-14070)', function() {
+    class TestSchemaType extends mongoose.SchemaType {}
+    TestSchemaType.set('validate', checkIfString);
+
+    const schemaType = new TestSchemaType('test-path', {
+      validate: checkIfLength2
+    });
+
+    assert.equal(schemaType.validators.length, 2);
+    assert.equal(schemaType.validators[0].validator, checkIfString);
+    assert.equal(schemaType.validators[1].validator, checkIfLength2);
+
+    let err = schemaType.doValidateSync([1, 2]);
+    assert.ok(err);
+    assert.equal(err.name, 'ValidatorError');
+
+    err = schemaType.doValidateSync('foo');
+    assert.ok(err);
+    assert.equal(err.name, 'ValidatorError');
+
+    err = schemaType.doValidateSync('ab');
+    assert.ifError(err);
+
+    function checkIfString(v) {
+      return typeof v === 'string';
+    }
+    function checkIfLength2(v) {
+      return v.length === 2;
+    }
+  });
+
   describe('set()', function() {
     describe('SchemaType.set()', function() {
       it('SchemaType.set, is a function', () => {